SHEAR INSTABILITY OF LONGSHORE CURRENTS: EFFECTS OF DISSIPATION AND NON-LINEARITY

Albert Falques, Vicente Iranzo, Miquel Caballeria

Abstract


The effect of bottom friction and turbulent lateral mixing on shear instability of the longshore current is investigated. Transition conditions for this instability as a function of non-dimensional parameters related to the basic current, topography, bottom friction and lateral mixing are found. A direct nonlinear numerical simulation of shear instability is presented. The basic flow is found to be supercritical and the amplitude of shear waves can reach at least 20% of the basic flow. A small increase in the period due to non-linearity is also found. Preliminary results suggest that far from criticality there is an important contribution of the instability to the mean flow. Some applications to field and laboratory experiments are discussed.

Keywords


shear instability; longshore current; current; dissipation; nonlinear current

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